Sandwich plate structures are common and known in such fields as aircraft and ship manufacture. Such structures can be comprised of two thin metallic or composite layers laminated onto a foam core. It is often necessary to attach various objects to these structures by means of screws. Such screws cannot be drilled through and fastened directly to the structure. The usual practice has been to drill a hole through the structure and then place an insert, usually metal with an axial bore, into the hole. The screw can then be inserted through the bore and attached to the structure.
The inserts used for these screw connections have several failings. In particular, they are prone to rotation within the structure, with consequent negative effects on the structure. Anchoring clamps have been used to prevent such rotation, but these are expensive and rely on the structure's skin to hold the insert in place.
When such clamps are too expensive or when the inserts must be installed flush with the metal or composite skins of the structure, direct "press fitting" of the inserts into holes drilled in the structure has been used. This has the disadvantage that only the structure's core prevents the insert from rotating. The skins of the structure do not grip the insert and are therefore unloaded.